Other Comprehensive Income (Reclassifications Out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Compensation and employee benefits	$ (37,554)	$ (35,700)	$ (107,737)	$ (96,095)
Net gain on securities transactions	27	0	257	55
Income tax expense	(12,913)	(9,285)	(44,417)	(18,257)
Total reclassification	37,268	27,143	130,618	56,384
Reclassification adjustment | Post- Retirement Obligations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Compensation and employee benefits	(149)	112	(449)	336
Income tax expense	38	(27)	119	(97)
Total reclassification	$ (111)	$ 85	(330)	239
Reclassification adjustment | Unrealized Gains (Losses) on Available for Sale Debt Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net gain on securities transactions			(230)	0
Income tax expense			59	0
Total reclassification			$ (171)	$ 0